Method for manufacturing separator

Abstract

A method for manufacturing a separator according to one aspect of the present disclosure is a method for manufacturing a separator including a flow path for a gas for generating electric energy and a bead having a gasket on the top, the method including: a step of forming a first convex portion corresponding to the flow path in a flat plate-shaped base material by performing press molding; the method includes a step of forming a first protrusion on a surface of a base material, a step of forming a surface layer on the surface of the base material on which the first protrusion is formed, a step of arranging a pad in a flat-plate-shaped protrusion formation region in the base material on which the surface layer is formed, the flat-plate-shaped protrusion formation region being provided with a protrusion, and a step of forming a second protrusion corresponding to the protrusion in a section in which the pad is arranged.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method for manufacturing a separator. BACKGROUND

[0002] A fuel cell is known that includes a fuel cell stack in which a plurality of unit cells are stacked. Fuel cells of this type are used in various applications, such as automobiles, factories, and homes, for example. Furthermore, generally, each of the plurality of unit cells in the fuel cell stack includes a metal separator provided with a gas flow path for a fuel gas (see Patent Literature 1 and Patent Literature 2, for example).

[0003] Patent Literature 3 discloses that each separator includes a convex ring that surrounds the gas flow path, which prevents leakage of the fuel gas. Patent Literature 4 discloses an elastic member provided on top of the convex ring to ensure the sealing performance of the gas flow path.

[0004] On the other hand, Patent Literature 5 discloses that, in order to maintain high electrical conductivity of the separator in a corrosive atmosphere in the unit cell, the base material of the separator is surface-treated to cause the surface of the base material to have a surface layer that enhances resistance to the corrosive atmosphere.

[0005] RELATED ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-66817

[0008] Patent Literature 2: Japanese Patent Application Laid-Open No. 2008-251296

[0009] Patent Literature 3: Japanese Patent Application Laid-Open No. 2020-198200

[0010] Patent Literature 4: Japanese Patent Application Laid-Open No. 2021-143676

[0011] Patent Literature 5: Japanese Patent Application Laid-Open No. 2022-85667 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] However, in a separator having a surface provided with a surface layer and a convex ring provided with a gasket such as an elastic member, there is room for improvement in the quality of the surface layer and the gasket. In view of the above, an object of the present disclosure is to improve the quality of the surface layer and the gasket.

[0014] MEANS FOR SOLVING THE PROBLEMS

[0015] A manufacturing method of a separator according to one aspect of the present disclosure is a manufacturing method of a separator including a flow path of a gas for generating electric energy and a boss provided with a gasket at a top, the method including: a step of forming a first protrusion corresponding to the flow path in a flat substrate by performing press molding; a step of forming a surface layer on a surface of the substrate in which the first protrusion is formed; a step of providing the gasket in a flat boss formation region in the substrate in which the surface layer is formed, the flat boss formation region being provided with the boss; and a step of forming a second protrusion corresponding to the boss in a section in which the gasket is provided.

[0016] Effects of the Invention

[0017] According to one aspect of the present disclosure, the quality of the surface layer and the gasket in the separator can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a plan view of an example of a schematic configuration of a fuel cell stack according to a first embodiment of the present disclosure.

[0019] Figure 2 is a partial cross-sectional view schematically showing a part of a cross section obtained by cutting the fuel cell stack in a thickness direction of a unit cell.

[0020] Figure 3 is a conceptual view showing an example of a manufacturing process of a separator according to the first embodiment.

[0021] Figure 4 is a conceptual view showing an example of a manufacturing process of a separator according to a second embodiment. DETAILED DESCRIPTION

[0022] Hereinafter, preferred embodiments according to the present disclosure will be described with reference to the accompanying drawings. Note that the size, the proportion, and the like of each element illustrated in the drawings can be different from those of actual elements, and some elements can be schematically illustrated for ease of understanding. Note that the scope of the present disclosure is not limited to the following description of the embodiments unless the following description includes a description specifically limiting the present disclosure. The scope of the present disclosure includes the equivalent scope of the following embodiments.

[0023] 1. First Embodiment

[0024] Configuration of Fuel Cell Stack and Unit Cell

[0025] Figure 1 is a plan view of an example of a schematic configuration of a fuel cell stack 10 according to the present embodiment. Furthermore, Figure 2 is a cross section taken along a line II-II shown in Figure 1 . Specifically, Figure 2is a partial cross-sectional view schematically showing a portion of a cross section obtained by cutting the fuel cell stack 10 in the thickness direction Z of the unit cell 11.

[0026] The fuel cell stack 10 is one of elements of a stacked polymer electrolyte fuel cell, and includes a plurality of unit cells 11, as shown in Figure 2 Each of the plurality of unit cells 11 generates electric energy through a chemical reaction of a fuel gas. In the present embodiment, the fuel gas is hydrogen, and each of the plurality of unit cells 11 converts chemical energy of hydrogen and oxygen as an example of oxidant gas into electric energy through a redox reaction. In the fuel cell stack 10, the plurality of unit cells 11 are electrically connected to each other, and electric energy from the respective unit cells 11 is collected to enhance the output of the fuel cell stack 10. A fuel cell including the fuel cell stack 10 is used for various applications, such as automobiles, household, and commercial uses.

[0027] As shown in Figure 1 In a plan view, each of the plurality of unit cells 11 has a shape of a rectangular plate, and as shown in Figure 2 In the fuel cell stack 10, the plurality of unit cells 11 are stacked one on another in the thickness direction Z. Each of the plurality of unit cells 11 includes a membrane electrode assembly 100, which is called a Membrane Electrode Assembly (MEA), and a pair of separators 200. The membrane electrode assembly 100 is sandwiched between the pair of separators 200 in the thickness direction Z. Thus, the pair of separators 200 constitutes a surface of the unit cell 11.

[0028] Note that, in the following description, two directions of a plane perpendicular to the thickness direction Z of the unit cell 11 are defined as a direction X and a direction Y. The direction X and the direction Y are perpendicular to each other. In other words, the direction X, the direction Y, and the thickness direction Z correspond to coordinate axes of a three-dimensional Cartesian coordinate system.

[0029] As shown in Figure 2 For example, the membrane electrode assembly 100 includes an electrolyte membrane 110 having a polymer membrane, an anode electrode layer 112, and a cathode electrode layer 114, as shown in For example, the electrolyte membrane 110 is a polymer electrolyte membrane. The membrane electrode assembly 100 is a stacked structure in which the electrolyte membrane 110 is sandwiched between the anode electrode layer 112 and the cathode electrode layer 114 in the thickness direction Z. Note that, although not shown, each of the anode electrode layer 112 and the cathode electrode layer 114 is a stacked structure including a catalyst layer formed on a central region of a surface of the electrolyte membrane 110 and a gas diffusion layer formed on the catalyst layer.

[0030] Each of the pair of separators 200 is a plate-like metal member. In the pair of separators 200, the separator 200 facing the anode electrode layer 112 of the membrane-electrode assembly 100 is provided with a first flow path 301 through which hydrogen gas flows between the first flow path 301 and the anode electrode layer 112. Further, the other separator 200 facing the cathode electrode layer 114 of the membrane-electrode assembly 100 is provided with a second flow path 302 through which oxygen gas flows between the second flow path 302 and the cathode electrode layer 114. Hydrogen gas is supplied to the anode electrode layer 112 through the first flow path 301, and oxygen gas is supplied to the cathode electrode layer 114 through the second flow path 302; thus, the membrane-electrode assembly 100 generates electric energy through the oxidation-reduction reaction of hydrogen gas. Note that, although not shown, the pair of separators 200 is also provided with flow paths for flowing a coolant.

[0031] Further, as shown in Figure 1 the pair of separators 200 is provided with a plurality of manifold holes 14 that penetrate therethrough from front to back. Each of the first flow path 301, the second flow path 302, and the coolant flow path is provided with a manifold hole 14, and hydrogen gas, oxygen gas, and a coolant are respectively supplied into the first flow path 301, the second flow path 302, and the coolant flow path through the corresponding manifold hole 14 and discharged from the other manifold hole 14.

[0032] Configuration of the separator

[0033] In the present embodiment, the pair of separators 200 has the same configuration. More specifically, as shown in Figure 2 the separator 200 includes a plurality of flow paths 310 each serving as the first flow path 301, the second flow path 302, or the coolant flow path, at least one bead 320, and a gasket 330 provided on the bead 320.

[0034] The plurality of flow paths 310 are grooves each having a concave shape ("C" shape) in cross section and extending parallel to each other in the X-Y plane, and the membrane-electrode assembly 100 is sandwiched between the corresponding separators 200 with the opening of each groove facing the anode electrode layer 112 or the cathode electrode layer 114 of the membrane-electrode assembly.

[0035] In a plan view of the separator 200, the bead 320 is a ring-shaped portion formed so as to surround all the flow paths 310 and has a function of sealing an inner space in the plan view. Specifically, as shown in Figure 2As shown, the ledge 320 includes a protrusion that protrudes largely in the thickness direction Z from other portions of the surface of the separator 200, and a gasket 330 is provided at the top thereof, as viewed in cross section along the thickness direction Z of the unit cell 11. In the stack of unit cells 11, the gasket 330 of one unit cell 11 is in contact with the gasket 330 of another unit cell 11, and the contact between the gaskets 330 causes sealing performance. Note that the ledge 320 is also provided at a position surrounding each manifold hole 14.

[0036] Further, the surface of the separator 200 is covered with a surface layer 350, and the surface layer 350 enhances corrosion resistance.

[0037] The separator 200 according to the present embodiment is a joined body of two plate-shaped metal substrates 400 joined to each other. The surface of each of the two substrates 400 is provided with a plurality of first protrusions 410 each of which is convex as viewed in cross section and corresponds to the flow path 310, and at least one second protrusion 420 each of which is convex as viewed in cross section and corresponds to the ledge 320. Here, when a front surface of the substrate 400 is defined as a surface provided in a direction in which the first protrusions 410 and the second protrusions 420 protrude, and a back surface of the substrate 400 is defined as a surface facing away from the front surface of the substrate 400, the separator 200 can be referred to as a joined body of the back surfaces of the two substrates 400 joined to each other, in other words, a joined body of the two substrates 400 joined back-to-back. In this joined body, grooves formed by adjacent first protrusions 410 correspond to the flow path 310. Further, the second protrusions 420 of the two substrates 400 are aligned in the thickness direction Z and face away from each other, thereby forming the ledge 320 that is substantially rectangular as viewed in cross section in both directions along the thickness direction Z. The top of each ledge 320 is provided with the gasket 330. According to this ledge 320, sealing performance in both directions along the thickness direction Z can be ensured. In other words, sealing performance between the membrane-electrode assembly 100 and the separator 200 in each unit cell 11 and sealing performance between the unit cells 11 can be ensured.

[0038] Method for manufacturing separator

[0039] Figure 3 is a conceptual view showing an example of a manufacturing process of the separator 200. First, a substrate 400 is prepared (step Sa1). As long as the substrate 400 is a plate member containing metal as a main material, the material of the substrate 400 can be freely selected. Typical examples of the plate member constituting the substrate 400 include a steel plate, a stainless steel plate, an aluminum plate, a titanium steel plate, and the like. Further, the manufacturing method of the plate member constituting the substrate 400 is not limited. Note that the above-described manifold hole 14 is formed in the substrate 400 in advance through an appropriate process.

[0040] Then, a plurality of first protrusions 410 are formed in the flow path formation region R1 of the substrate 400 in which the flow path 310 is to be provided (step Sa2). For example, the plurality of first protrusions 410 are formed by first press molding. The first press molding is performed by sandwiching the substrate 400 between a first male die 611 and a first female die 612 and applying a pressure between the first male die 611 and the first female die 612. The first male die 611 includes protrusions corresponding to the first protrusions 410. The first female die 612 includes recesses for receiving the protrusions of the first male die 611.

[0041] Then, the surface of the substrate 400 is subjected to surface treatment (step Sa3). The surface treatment is a treatment for forming the surface layer 350 on the surface of the substrate 400. The method of the surface treatment can be freely selected; for example, the vapor deposition treatment or the reduction treatment disclosed in Patent Literature 5 can be used. Figure 3 A manner in which the substrate 400 is placed in the chamber 700 and the surface layer 350 is deposited by vapor deposition is shown.

[0042] According to the manufacturing procedure of the present embodiment, the surface layer 350 is formed on the substrate 400 after the first press molding that forms the first protrusions 410 that constitute the flow path 310. Therefore, compared to a case in which the surface layer 350 is formed before the first press molding, it is possible to prevent the first press molding from causing the surface layer 350 to peel off or be damaged (for example, cracked), thereby maintaining the high quality of the surface layer 350. As a result, it is possible to prevent a decrease in the corrosion-resistant atmosphere due to degradation of the surface layer 350.

[0043] Then, before the second protrusions 420 corresponding to the beads 320 are formed, the gasket 330 is provided in the bead formation region R2 of the substrate 400 in which the beads 320 are to be provided (step Sa4). As the material of the gasket 330, a rubber material such as silicone, fluorine, or ethylene propylene diene rubber (EPDM) is used. Furthermore, the width W and the thickness of the gasket 330 are appropriate. For example, the width W of the gasket 330 according to the present embodiment is less than or equal to 5 mm, and the thickness is less than or equal to 200 μm. For example, the gasket 330 is formed by applying the rubber material using a dispenser.

[0044] In this step Sa4, the bead formation region R2 maintains a flat plate shape. Therefore, for example, compared to a case in which the gasket 330 is provided on a surface that can include a bend or a concave-convex (such as the top of the second protrusion 420), it is possible to form the gasket 330 with high precision and maintain the high quality of the gasket 330. As a result, it is possible to prevent a decrease in the sealing performance due to degradation of the gasket 330.

[0045] Then, in the portion of the gasket formation region R2 in which the gasket 330 is provided, a second protrusion 420 is formed (step Sa5). For example, the second protrusion 420 is formed by second press molding. The second press molding is performed by sandwiching the base material 400 between a second male mold 621 and a second female mold 622 and applying pressure between the second male mold 621 and the second female mold 622. The second male mold 621 includes a protrusion corresponding to the second protrusion 420. The second female mold 622 includes a recess for receiving the protrusion of the second male mold 621 and a recess for receiving the first protrusion 410 formed in step Sa2.

[0046] Then, the two base materials 400 subjected to the processes from step Sa1 to step Sa5 are joined to each other (step Sa6). Specifically, the back surfaces of the two base materials 400 are joined to each other. The joining method can be freely selected; for example, welding or the like can be used. This step Sa6 results in a plurality of flow paths 310 and a partition 200 including the gasketed ring 320 with the gasket 330. Note that the processes including steps Sa1 to Sa5 are an example of a "first process", and step Sa6 is an example of a "second process".

[0047] As described above, the manufacturing process of the partition 200 according to the present embodiment includes a process of forming the first protrusion 410 corresponding to the flow path 310 in the base material 400 of the partition 200 by performing press molding (step Sa2), a process of forming the surface layer 350 on the surface of the base material 400 in which the first protrusion 410 is formed (step Sa3), a process of providing the gasket 330 in the flat plate-shaped ring formation region R2 of the base material 400 in which the surface layer 350 is formed, the flat plate-shaped ring formation region R2 being provided with the ring 320 (step Sa4), and a process of forming the second protrusion 420 corresponding to the ring 320 in the portion provided with the gasket 330 (step Sa5), and these processes are performed in this order.

[0048] According to this manufacturing process, compared to the case where the surface layer 350 is formed before the first protrusion 410 is formed by press molding, it is possible to prevent the surface layer 350 from being peeled off or damaged (for example, cracked) by the formation of the first protrusion 410 by press molding, and to prevent a decrease in corrosion-resistant atmosphere.

[0049] In addition to this, according to the present embodiment, the gasket 330 is formed in the flat plate-shaped ring formation region R2 in which the curvature is less and the unevenness is less. As a result, it is possible to provide the gasket 330 in the portion in which the ring 320 is to be provided with high precision, and to prevent a decrease in sealing performance due to insufficient precision of the gasket 330.

[0050] Further, the manufacturing process of the separator 200 according to the present embodiment includes a process of joining the two substrates 400 to each other, the two substrates each being provided with the first protrusions 410 and the second protrusions 420, the top of the second protrusion 420 being provided with the gasket 330.

[0051] According to the manufacturing process, it is possible to obtain the separator 200 including the beads 320 each having a substantially rectangular cross section, the beads 320 being protruded in both directions along the thickness direction Z, the top of the bead 320 being provided with the gasket 330. According to the separator 200, it is possible to make the beads 320 ensure the sealing performance in both directions along the thickness direction Z. In other words, it is possible to ensure both the sealing performance between the membrane electrode assembly 100 in each unit cell 11 and the separator 200 and the sealing performance between the unit cells 11.

[0052] 2. Second Embodiment

[0053] Figure 4 is a conceptual view illustrating an example of a manufacturing process of the separator 200 according to the first embodiment. Note that, in Figure 4 , elements that have been explained in the first embodiment have the same reference numerals, and the explanation thereof is omitted. Note that, in the second embodiment, the step Sa1 and the step Sa2 are implemented as in the first embodiment; however, in Figure 4 , for convenience, the step Sa1 and the step Sa2 are omitted.

[0054] As Figure 4 illustrated, the manufacturing process according to the present embodiment includes, after the process of forming the skin layer 350 (step Sa3) and before the process of forming the gasket 330 (step Sa4), a process (step Sb1) of forming a third protrusion 430 in the bead formation region R2 by third compression molding. The third protrusion 430 has a flat top and is a segment having a protrusion shape when viewed in a cross section. Specifically, the height H of the third protrusion 430 is greater than or equal to the height of the first protrusion 410 and less than or equal to the height of the second protrusion 420. Note that, in Figure 4 , the height H of the third protrusion 430 is substantially equal to the height of the first protrusion 410. After the above step Sb1, the gasket 330 is formed in the step Sa4.

[0055] In the step Sb1, the third compression molding is implemented by sandwiching the substrate 400 between a third male mold 631 and a third female mold 632 and applying a pressure between the third male mold 631 and the third female mold 632. The third male mold 631 includes a protrusion corresponding to the third protrusion 430. The third female mold 632 includes a recess for receiving the protrusion of the third male mold 631 and a recess for receiving the first protrusion 410 formed in the step Sa2.

[0056] By implementing the step Sb1, the height H of the section of the gasket 330 is greater than or equal to the height of the first protrusion 410. Here, in a case where screen printing is used instead of the dispenser described in the first embodiment to form the gasket 330, the formation is implemented in a state where a squeegee presses a screen, a portion of which is provided with an opening in advance in correspondence with the section of the gasket 330 to which material is to be applied, to the section of the gasket 330 to be formed and brings the screen into close contact with the section. However, if the first protrusion 410 is higher than the gasket 330, the first protrusion 410 interferes with the screen; thus, the screen cannot be brought into close contact with the section of the gasket 330 to be formed. In contrast, according to the present embodiment, since the height H of the section of the gasket 330 to be formed is greater than or equal to the height of the first protrusion 410, it is possible to perform screen printing on the base material 400 to form the gasket 330 without interference from the first protrusion 410. Thus, by causing the portion of the screen provided with the opening in advance to correspond to the section to which the gasket is to be applied, it is possible to apply the material to be the gasket 300 at a time in a wide range. As a result, it is possible to reduce the tact time required to form the gasket 330.

[0057] Here, as shown in a cross section along the thickness direction Z, the protrusion ring formation region R2 has a width that at least sufficiently contains the protrusion ring 320. Further, when a plurality of protrusion rings 320 are provided side by side, the protrusion ring formation region R2 has a width that contains all of the plurality of protrusion rings 320. In other words, the width of the protrusion ring formation region R2 is sufficiently wide compared to each of the protrusion rings 320, and the shape of the top of the third protrusion 430 formed by the third compression molding maintains a flat plate shape.

[0058] In other words, even in the manufacturing process according to the present embodiment, as with the first embodiment, the second protrusion 420 corresponding to the protrusion ring 320 is formed after the gasket 330 is provided in the flat plate-shaped protrusion ring formation region R2. Thus, it is possible to provide a gasket 330 of high precision to prevent a decrease in sealing performance due to insufficient precision of the gasket 330.

[0059] 3. Modified Example

[0060] Hereinafter, specific modified examples that can be added to the above-described first and second embodiments will be described. Two or more modified examples selected freely from the following modified examples can be combined as long as such a combination does not cause a conflict.

[0061] (1) In each of the embodiments, the partition 200 in which two base materials 400 are joined to each other is described. However, the partition 200 can be constituted by a single base material 400. In this case, the first protrusion 410 corresponds to the flow path 310, and the second protrusion 420 corresponds to the protrusion ring 320.

[0062] (2) The manufacturing materials and methods described in each embodiment can be appropriately modified without departing from the spirit of the present disclosure.

[0063] (3) In this disclosure, the term "nth" (n is a natural number) is used merely as a convenient label to distinguish elements in the description and has no substantial meaning. Therefore, the position of each element, the order in which the elements are produced, etc. are not limited by the reference to the term "nth."

[0064] Description of Reference Numerals

[0065] 10…fuel cell stack, 11…unit cell, 100…membrane electrode assembly, 200…separator, 310…flow path, 320…protrusion, 330…gasket, 350…surface layer, 400…substrate, 410…first protrusion, 420…second protrusion, 430…third protrusion, H…height, R2…protrusion formation area, Z…thickness direction.

Claims

1. A method for manufacturing a separator, the separator comprising a flow path for a gas used to generate electrical energy and a raised ring with a gasket disposed on top, the method comprising: forming a first protrusion corresponding to the flow path on the flat plate-shaped substrate by performing compression molding; forming a surface layer on the surface of the substrate on which the first protrusions are formed; The step of providing the gasket in a flat plate-shaped bead forming region of the base material having the surface layer formed thereon, the bead being provided in the flat plate-shaped bead forming region; and a step of forming a second protrusion corresponding to the protruding ring in the section where the gasket is provided.

2. The method for manufacturing a separator according to claim 1, in, The process of setting the liner includes: forming a third protrusion in the bead forming region by die-casting, wherein the third protrusion has a flat top and a height of the third protrusion is less than or equal to a height of the second protrusion; a step of placing the gasket on the flat top portion of the third protrusion; and and forming the second protrusion corresponding to the bead in the section where the gasket is provided.

3. The method for manufacturing a separator according to claim 1, in, The process of setting the liner includes: forming a third protrusion in the bead forming region by press molding, wherein the third protrusion has a flat top and a height greater than or equal to that of the first protrusion and less than or equal to that of the second protrusion; a step of placing the gasket on the flat top portion of the third protrusion; and and forming the second protrusion corresponding to the bead in the section where the gasket is provided.

4. A method for manufacturing a separator, the method comprising: A first step of forming a flow path for a gas used to generate electricity and a raised ring with a gasket provided on top in each of two flat plate-shaped substrates; and a second step of joining the two substrates after the first step is completed, Wherein, for any one of the two substrates, the first process includes: forming a first protrusion corresponding to the flow path in the substrate by performing compression molding; forming a surface layer on the surface of the substrate on which the first protrusions are formed; The step of providing the gasket in a flat plate-shaped bead forming region of the base material having the surface layer formed thereon, the bead being provided in the flat plate-shaped bead forming region; and a step of forming a second protrusion corresponding to the protruding ring in the section where the gasket is provided.

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